select positionChild,(select Remark from Freqs a join Contents b on a.ID=b.senior where b.ID=c.id) as senior,
  (select Remark from Freqs a join Contents b on a.ID=b.middle where b.ID=c.id ) as middle,
  (select Remark from Freqs a join Contents b on a.ID=b.general where b.ID=c.id ) as general
    from Contents c

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